This invention relates to reciprocating internal combustion engines and in particular, but without limitation to higher efficiency regenerative cycle internal combustion engines in which the principles of isothermal compression and regeneration of exhaust gas heat can be applied as far as is practical.
The requirement to obtain maximum efficiency from reciprocating internal combustion engines has always been of interest to the designer but additional considerations of simplicity, reliability and ease of manufacture must all be factored in to produce an affordable engine sufficiently rugged to meet the demands of general public use. Therefore, it is of little surprise to observe that all attempts to bring into mass production reciprocating engines working on the highest possible efficiency cycles such as the Stirling and Ericsson cycles have failed. In fact, considerable resources have been committed to developing a practical Stirling cycle engine but to date the efforts have failed to deliver both the hoped for theoretical efficiency, or the reliability, demanded by commercial enterprise. However, the present world climate with massively increased daily use of vehicular transport by the developing nations, coupled with finite fossil fuel supplies, burgeoning levels of exhaust emissions, and global warming, now places an urgent demand for a simple, affordable and rugged reciprocating engine which can work as closely to the maximum ideal thermodynamic cycles as is practically possible. In addition, such an engine should be capable of maximising the efficiency of the overall driving cycle by conserving vehicular kinetic energy during braking by utilisation of regenerative braking. In addition, the engine should be capable of taking full advantage of spare electricity grid capacity during off peak hours to store energy for daily use. In addition, the engine should be capable of meeting exhaust emissions limits by reducing peak cycle temperatures. The Phased Induction Regenerative Engine herein described is fully capable of meeting these demands.
Internal combustion engines generally comprise a piston arranged to reciprocate within a cylinder and the piston is connected, via a connecting rod, to a crank shaft such that the reciprocating movement of the piston within the cylinder is converted into rotational movement of the crank shaft. The crank shaft is usually directly connected, or indirectly connected via a gearbox, to an output shaft, such that a useful rotating output can be obtained from the engine.
Most internal combustion engines are driven by the explosive force of a charge (usually comprising a fluid fuel/air mixture) ignited within the cylinder, which drives the piston downward to rotate the crank shaft. The ignition of charge causes it to expand rapidly, thus creating a high positive pressure within the cylinder to force the piston downwards. Even with the advances in modern engine technology that enable the introduction and composition of the charge to be carefully timed and controlled, the ignition/power stroke of most internal combustion engines is still relatively thermodynamically inefficient.
The structure of an internal combustion engine must be designed to withstand the high pressures, forces and temperatures involved in the ignition/power stroke of the engine. Given that the power stroke is the heaviest duty cycle of the engine, and the stroke that gives rise to the useful output, the majority of the design considerations associated with internal combustion engines are focused in this area.
On the other hand, however, there is a competing requirement that detracts from the overall efficiency of the engine, namely the compression stroke, whereby the same engine components are configured to compress the charge prior to ignition. In almost all engines, the compression stroke is performed using the same apparatus as the power stroke, namely the piston and cylinder arrangement previously described, whereby the inertia of the crank shaft (and its associated flywheel and/or connected equipment) is used to drive the piston upwards within the cylinder to compress the charge prior to ignition. The fundamental problem with this arrangement is that the adiabatic heat of compression raises the charge temperature to such a degree that any gain from regenerative use of heat from the exhaust will add very little to overall cycle efficiency.
As such, there are two inherent flaws in the design and construction of known internal combustion engines, namely that: the engine must compress the charge adiabatically in each cycle, which not only increases the work used during the compression stroke but also raises the charge temperature to such a degree that the extra complexity required to regeneratively make use of exhaust heat is not justified.
A need therefore arises for a new type of internal combustion engine that addresses one or more of the above problems and which provides an improved and/or alternative internal combustion engine, and ideally, an engine whose construction lends itself to additional features such as regenerative braking, off peak storage of energy from the electricity grid or indeed any energy source which can compress air.